This is the final chapter “Coda” from the book Denial by Ajit Varki and Danny Brower.
Any theory that makes progress is bound to be initially counterintuitive. ––Daniel C. Dennett, in The Intentional Stance
Some readers may wish to skip this final section. But those who wish to revisit and ponder the underlying concept in this book may find it useful to read the following formal summary of the Mind over Reality theory for the evolutionary emergence of the human mind.
- Each species on the planet is unusual in its own right. Humans are rather unusual in the way our brains work. One key feature is that we can put ourselves in the mental shoes of others, thus understanding each other’s minds, thoughts, and actions and then easily imitating them if we wish to. This ability has allowed humans to transmit complex and increasingly sophisticated cultures and technologies to future generations, aided by various means of communication, most especially language.
- Many other warm-blooded, socially complex mammals and birds are also capable of remarkable feats of intelligence and cognition. Available evidence suggests that some such species are similar to humans in being self-aware—like us, they seem to be aware of themselves as individual minds and thus perhaps are able to understand their own personhoods.
- Despite such abilities, none of these species appears capable of fully understanding the self-awareness of others of their own kind—or, further, capable of understanding that others are aware of their own self-awareness. This ability to fully attribute mental states to others is sometimes called full theory of mind (ToM). Such a capacity so far appears to be uniquely human and is critical to many of the unusual features of our minds. We humans go further, in that we can hold an extended ToM of many individuals—and even, based on secondhand information, understand the minds of others we have not met.
- Without this full and extended ToM, much of what the human mind can and has achieved would not be possible. Why is it that only humans achieved this powerful ability, while other species with self-awareness did not? Broadly considered, there are two possibilities.
- The first possibility (the conventional view) is that the neural mechanisms required were most unusual, involving an extremely rare combination of molecular and cellular changes in the brain, which only happened once during evolution. In this logic, it is assumed that full ToM was an immediately useful attribute, providing humans with a unique and powerful ability to understand the minds of others. Conventional natural selection would then take over, increasing the likelihood of such individuals passing on their genes. Additional improvements in ToM would then occur by further positive selection. This is the currently popular theory, and many candidate mechanisms have been explored and discussed. However, no such mechanisms have yet been clearly defined as being unique to humans, in comparison to our closest evolutionary cousins.
- The alternate possibility (the unconventional, contrarian view presented here) is that the initial acquisition of full ToM (becoming fully aware of the self-awareness and personhood of others) actually had immediately negative consequences for the individual. Thus the capacity to sustain and propagate this ability within any species may have been repeatedly blocked by a psychological evolutionary barrier that only humans finally transcended. Assuming the latter possibility is correct, what might this barrier have been?
- All animals have built-in reflex mechanisms for fear responses to dangerous or life-threatening situations. An individual of a given species who attains full ToM for the first time will also for the first time fully understand the personhood of other individuals of its own kind. At first glance this would seem a positive attribute, allowing one to control or even deceive others. But upon then witnessing the death of another individual of its own kind, the one with full ToM would also become aware of his or her own mortality and death risk (mortality salience).
- Given the preexisting built-in mammalian reflex mechanisms for reacting to death risk, this new knowledge of mortality should induce an extreme degree of fear. A present-day human can deal with such fears by rationalizing and calibrating the risk. But the first individuals to understand mortality would not be able to rationalize or understand the fear—because there would be no prior knowledge base to go on and also because there would not necessarily be any other individuals with whom to commiserate or discuss the death risk. A deep fear and anxiety would result, perhaps progressing to depression and even to suicidal tendencies.
- Thus, rather than take advantage of the obvious benefits of full ToM, the individual is more likely to avoid all potential death risks, including those involved in competition with others for resources and mates. In other words, individual personal survivalwould take priority over behavioral drives that typically ensure species survival. The individual would thus be unlikely to succeed in the competition to pass on his or her genes to the next generation—there would be initial negative and not positive selection for this trait.
- Beyond this psychological evolutionary barrier, another factor limits the possibility of establishment of full ToM in a species. There is no evidence for a single gene or molecule responsible for this ability in humans. Rather, it is likely that this complex ability results from optimal interactions among a suite of genes and molecular and cellular mechanisms. Thus, in order to pass on this ability to the next generation, it would likely be necessary for more than one individual of both sexes to develop this ability at about the same time, and the ability would eventually need to become genetically stabilized in a population of individuals.
- Taken together, the above combination of factors makes it highly unlikely that full ToM could become easily established in a species. It is quite possible that such episodes of appearance and disappearance of full ToM have been occurring in many species for tens of millions of years, until humans finally breached this psychological evolutionary barrier. How did humans achieve this?
- One plausible mechanism that would allow escape from this psychological evolutionary trap would be for individual(s) with ToM to simultaneously attain the ability to deny mortality and death risk. This would require neural mechanisms to diminish the deep fears arising from understanding mortality.
- However, simultaneously evolving a highly selective neural mechanism for suppressing fear of mortality would be difficult. A general mechanism to deny reality (including the risk of mortality) is more likely. This possibility has the additional advantage that it does not require generation of a new neural module. Rather, it could simply result from partial alterations to existing pathways for classical fear responses. Once this happened, selective inattention to death risk would also become possible.
- Notably, general reality denial and suppression of mortality fears are not by themselves positive features for an individual member of a species because of the danger of inappropriately risky behavior. Meanwhile, we have already said that acquiring a full ToM and understanding mortality would also be a negative feature at first. But the simultaneous occurrence of these two negative attributes in the same individuals would cancel each other out, allowing those developing a full ToM to survive and propagate by denying mortality risk.
- Once this combination became established in a small population, individuals with both abilities would have many positive benefits. For one thing, they would have all the benefits of full ToM, including the ability to understand and relate to each other—and they would also likely eschew mating with others who did not. In addition, reality denial also allows the emergence of optimism and overconfidence, which at a reasonable level can have many benefits and advantages to the individual and to the species.
- Thus the Mind over Reality theory posits that humans are the only extant species with full ToM because we are the only ones who crossed the evolutionary psychological barrier of living with the knowledge of our mortality by simultaneously acquiring the mental ability to deny reality.
- While it is currently not possible to falsify this hypothesis, it appears consistent with all available information. It can also explain a wide range of uniquely human features, such as risky behavior, the optimism bias, depressive realism, suicide, religiosity, existential angst, bravery, empathy, indirect reciprocity, and so on. And while there are many facts that fit with this theory, none appears as yet to directly militate against it.
- It is of course possible that full ToM appeared somewhat more gradually, coevolving step-by-step over time with denial of reality in the founder population of behaviorally modern humans. However, given the negative consequences and relative instability of each individual state, this coevolution could not have gone on for a very long time.
- Regardless of how the individual steps occurred, there should be an underlying neural basis for this unusual combination of cognitive and psychological features. In this regard it is interesting that the regions of the brain implicated in human ToM (the frontal cortex and its adjacent structures) are also the ones generally involved in executive control of both fear and optimism via interactions with the amygdala. Further studies could address the possibility that emergence of the neural substrate of a full ToM may have incidentally and partially altered pathways from the frontal cortex to the amygdala that mediate normal fear responses and conditioning, perhaps allowing a blunting of such responses. Meanwhile, it is intriguing that these brain areas are unusually modified in humans and are affected in some relevant mental disease states.
- Finally, taking all available information into consideration, the most likely timing of the proposed evolutionary transition would have been just prior to the emergence of behaviorally modern humans in Africa, currently estimated at around one hundred thousand years ago. Since the original effective population size of all living humans is estimated to be around five to ten thousand, the Mind over Reality transition that occurred first in a few individuals must have initially spread to others via breeding during this early phase. Once established, this population with a potent combination of novel mental abilities would then have gradually spread over the planet, eventually replacing other existing humanlike subspecies, with whom there was only limited and ineffective interbreeding.